(1). Field of the Invention
The present invention relates to an isolated sensing device and in particular, to a flow noise isolation housing for isolating flow noise from a hydrophone.
(2). Description of the Prior Art
The measurement of underwater sound is of increasing interest, particularly in underwater direction and range finding equipment (e.g., sonar). Sound is created in a water environment by a source of acoustic energy that generates an acoustic pressure field in the water. The sound pressure level is typically measured with pressure measuring or sensing devices, such as underwater microphones or hydrophones.
One difficulty with underwater measurements of a sound pressure level is the adverse affect of fluid flow noise on the sound measurement by a hydrophone. When fluid flows over the hydrophone, pressure fluctuations caused by the flow are sensed in addition to the acoustic pressures generated by the acoustic energy source. The resulting sound pressure level measurements are distorted and unclear as a result of the affect of the non-acoustic pressure fluctuations or "flow noise" caused by the flowing fluid, similar to the effect created by blowing over a microphone. Existing hydrophones do not accurately measure acoustic pressure or sound in an underwater environment because this flow noise is not effectively isolated from the hydrophone.